Research Article Effect of Sulfation on Zirconia-Pillared Montmorillonite to the Catalytic Activity in Microwave-Assisted Citronellal Conversion Is Fatimah, 1 Dwiarso Rubiyanto, 1 and Thorikul Huda 2 1 Chemistry Department, Islamic University of Indonesia, Kampus Terpadu UII, Jl. Kaliurang Km 14, Sleman, Yogyakarta 55581, Indonesia 2 Professional Program of Chemical Analyst Department, Islamic University of Indonesia, Kampus Terpadu UII, Jl. Kaliurang Km 14, Sleman, Yogyakarta 55581, Indonesia Correspondence should be addressed to Is Fatimah; isfatimah@uii.ac.id Received 17 February 2014; Revised 20 June 2014; Accepted 23 June 2014; Published 10 July 2014 Academic Editor: Deepak Kunzru Copyright © 2014 Is Fatimah et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Preparation of sulfated zirconia-pillared montmorillonite was carried out in two steps; zirconia pillarization and sulfation to zirconia-pillared montmorillonite. Te prepared materials were characterized by using X-ray difraction (XRD), measurement of the specifc surface area, total pore volume and pore size distribution by the N 2 adsorption method, scanning electron microscopy- energy dispersive X-ray (SEM-EDX), and surface acidity determination by using pyridine adsorption-FTIR analysis. Te activity of the materials as catalysts was evaluated for a microwave-assisted conversion of citronellal. Te results showed that the prepared materials had a physicochemical character that promoted high catalytic activity to convert citronellal. From varied Zr content and study of the efect of sulfation on the activity, it was found that Zr content and sulfation increase the surface acidity of the material as shown by the higher total conversion and tendency to produce menthol as a product of the tandem cyclization-hydrogenation mechanism. 1. Introduction Isopulegol is a very important intermediate in several chem- ical production processes including menthol production by the Takasago process. Te cyclization reaction of citronellal to isopulegol is the main route in the conversion of some impor- tant favors and chemical intermediates and for environmen- tal reasons; some heterogeneous catalysts for the reaction have been studied. A number of heterogeneous catalysts have also been reported to be active in citronellal conversion such as zeolite beta, MCM-41, HY, mordenite, mixed oxides of SiO 2 -TiO 2 , SiO 2 -ZrO 2 , and SiO 2 -Al 2 O 3 with and without copper, sulfated zirconia, and metal cation-exchanged mont- morillonites [1] Among these materials, zirconia and sulfated zirconia have been receiving much attention due to their solid acidity and chemical stability as well as the thermal stability and superiority in hydrocarbon conversions such as in alkylation, cyclization, and isomerization [2–5]. A previous report showed that S-ZrO 2 catalyses the cycli- sation of citronellal with high conversion and selectivity [6]. Considering the eco-friendly process, some investigations have considered either zirconia immobilized solid support or the use of zirconia as metal support. In case of immobiliza- tion, sulfation of zirconia can be performed to produce higher solid acidity in relevance with higher conversion in organic reaction mechanisms including cyclization. Referring to the physicochemical properties of montmorillonite mineral hav- ing a high specifc surface area and porous structure, this research is aimed at combining the advantages of sulfation and immobilization. Tis work investigates the preparation, characterization, and catalyst activity of sulfated zirconia- immobilized montmorillonite material. Based on the surface acidity and porous structure of the montmorillonite structure enhanced by pillarization and sulfation which are impor- tant characteristics of heterogeneous catalysis, the combined modifcation is hypothesized to signifcantly improve catalyst activity and selectivity as well as the reusable properties of the catalyst. Preparation is based the scheme of in situ prepa- ration of sulfated zirconia and in situ sulfated zirconia clay Hindawi Publishing Corporation International Journal of Chemical Engineering Volume 2014, Article ID 950190, 7 pages http://dx.doi.org/10.1155/2014/950190